An ethylene-tetrafluoroethylene copolymer (hereinafter referred to also as “ETFE”) is used in a wide range of fields including automobile components, plastic greenhouses for agriculture, building materials, etc. ETFE is usually produced by solution polymerization of monomers in a fluorinated organic solvent as a polymerization medium. In such a method, a slurry having a relatively high viscosity is obtained wherein ETFE microparticles are suspended. Then, volatile components such as non-reacted monomers, the polymerization medium, etc. are recovered from the slurry, to obtain a powder of ETFE (hereinafter referred to as an “ETFE powder”). By minimizing the residual amount of volatile components in the ETFE powder, it is possible to suppress bubbling at the time of molding the ETFE powder, whereby the processability will be improved. Further, by recovering volatile components from the slurry at a high recovery rate and reusing them, the costs can be reduced.
As methods for producing an ETFE powder by recovering volatile components from the slurry, the following methods (1) and (2) are known.
(1) A method wherein the slurry is subjected to filtration by a glass filter to separate ETFE, which is then heated to vaporize and recover volatile components and to obtain an ETFE powder (Patent Document 1).
(2) A method wherein the slurry is added to water, followed by stirring and heating in such a state that the slurry is dispersed in water, to vaporize and recover volatile components, and then, an operation for solid-liquid separation of ETFE and water is carried out, followed by drying to obtain an ETFE powder (Patent Document 2)